Mo. Rev. Stat. § 524.170: Petition — contents.

The plaintiff in his petition shall set forth the nature of his title, the length of his possession and the kind and value of the improvements made; and shall also aver therein that he entered into the possession of the land, believing that he had good title thereto, and that he made the improvements specified in the petition in good faith, under the belief that he had good title to the land, and shall be verified by his affidavit thereto annexed.